Dotnet framework interview questions and answers

 

1. What is the .NET Framework?

• The .NET Framework is a software development platform developed by Microsoft.
• It provides a consistent programming model and a comprehensive set of libraries to build various applications such as web, desktop, and mobile apps.
• It consists of two major components:
  • Common Language Runtime (CLR): Handles memory management, exception handling, and garbage collection.
  • .NET Framework Class Library (FCL): Provides reusable classes and APIs for development.

Example:

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, .NET Framework!");
    }
}

2. What is the Common Language Runtime (CLR)?

• CLR is the heart of the .NET Framework, responsible for executing .NET programs.
• It provides key services:
  • Memory management (using garbage collection).
  • Exception handling.
  • Thread management.
  • Security management.

Key Features of CLR:

• Just-In-Time (JIT) Compilation: Converts Intermediate Language (IL) code to machine code.
• Garbage Collection (GC): Automatically frees memory by removing objects that are no longer in use.

Example:

public class Example
{
    public void ShowMessage()
    {
        Console.WriteLine("CLR manages this execution.");
    }
}

3. What is the difference between .NET Framework and .NET Core?

• .NET Framework:
  • Runs only on Windows.
  • Used for building Windows-specific applications like desktop apps.
  • Larger runtime and library support.
• .NET Core:
  • Cross-platform (supports Windows, Linux, macOS).
  • Lightweight and modular.
  • Primarily used for web, cloud, and cross-platform apps.

4. What are Assemblies in .NET?

• Assemblies are the building blocks of a .NET application.
• An assembly is a compiled code that CLR can execute. It can be either an EXE (for applications) or a DLL (for reusable components).

Types of Assemblies:

• Private Assembly: Used by a single application.
• Shared Assembly: Can be shared across multiple applications (e.g., libraries stored in GAC).

Example:

// Compiling this code will create an assembly (DLL or EXE)
public class SampleAssembly
{
    public void DisplayMessage()
    {
        Console.WriteLine("This is an assembly example.");
    }
}

5. What is the Global Assembly Cache (GAC)?

• GAC is a machine-wide code cache that stores assemblies specifically designated to be shared by several applications on the computer.
• Assemblies in GAC are strongly named and allow multiple versions of the same assembly to be maintained side by side.

Example:

// To add an assembly to the GAC (in command prompt)
gacutil -i MyAssembly.dll

6. What are Namespaces in .NET?

• Namespaces are used to organize classes and other types in .NET.
• They prevent naming conflicts by logically grouping related classes.

Example:

namespace MyNamespace
{
    public class MyClass
    {
        public void Greet()
        {
            Console.WriteLine("Hello from MyNamespace!");
        }
    }
}

7. What is Managed Code?

• Managed Code is the code that runs under the control of the CLR.
• CLR manages execution, garbage collection, and other system services for the code.

Example:

// This is managed code because it's executed by CLR
public class ManagedCodeExample
{
    public void Print()
    {
        Console.WriteLine("Managed Code Example.");
    }
}

8. What is Unmanaged Code?

• Unmanaged Code is code executed directly by the operating system, not under the control of CLR.
• Examples include applications written in C or C++ that are compiled directly into machine code.

Example:

// Calling unmanaged code from C#
[DllImport("User32.dll")]
public static extern int MessageBox(IntPtr hWnd, String text, String caption, int options);

9. What is the difference between Value Types and Reference Types in .NET?

• Value Types:
  • Stored directly in memory.
  • Examples: int, float, bool.
• Reference Types:
  • Store a reference (pointer) to the actual data in memory.
  • Examples: class, object, string.

Example:

// Value type
int x = 10;

// Reference type
string name = "John";

10. What is Boxing and Unboxing in .NET?

• Boxing: Converting a value type to an object (reference type).
• Unboxing: Extracting the value type from an object.

Example:

// Boxing
int num = 123;
object obj = num;  // Boxing

// Unboxing
int unboxedNum = (int)obj;  // Unboxing

 

11. What is the Common Type System (CTS)?

• CTS defines all data types in the .NET Framework and how they are represented in memory.
• It ensures that data types used across different .NET languages (C#, VB.NET, F#) are compatible with each other.
• Value Types (stored in the stack) and Reference Types (stored in the heap) are both part of CTS.

Example:

// Value type
int valueType = 100;

// Reference type
string referenceType = "Hello";

12. What is the Common Language Specification (CLS)?

• CLS defines a subset of the Common Type System (CTS) that all .NET languages must follow to ensure cross-language compatibility.
• It provides a set of rules for data types and programming constructs that are guaranteed to work across different languages.

Example:

 // CLS-compliant code: using standard types
public class SampleClass
{
    public int Add(int a, int b)
    {
        return a + b;
    }
}

 

13. What is Just-In-Time (JIT) Compilation?

• JIT Compilation is a process where the Intermediate Language (IL) code is converted to machine code at runtime.
• It helps optimize execution by compiling code only when it is needed, thus saving memory and resources.

Types of JIT Compilers:

• Pre-JIT: Compiles the entire code during deployment.
• Econo-JIT: Compiles only required methods, reclaims memory afterward.
• Normal JIT: Compiles methods when called for the first time.

 

 

14. What is the difference between Early Binding and Late Binding in .NET?

• Early Binding:

  • Happens at compile time.
  • Compiler knows the method signatures and types in advance.
  • Safer and faster.

• Late Binding:

  • Happens at runtime.
  • Uses reflection to dynamically invoke methods and access types.
  • Flexible but slower and prone to errors.

Example:

 // Early binding
SampleClass obj = new SampleClass();
obj.PrintMessage();

// Late binding using reflection
Type type = Type.GetType("SampleClass");
object instance = Activator.CreateInstance(type);
MethodInfo method = type.GetMethod("PrintMessage");
method.Invoke(instance, null);

 

15. What is Garbage Collection (GC) in .NET?

• Garbage Collection is the process in the .NET Framework that automatically frees memory by reclaiming objects that are no longer in use.
• GC improves memory management by cleaning up unreferenced objects.

Generations in Garbage Collection:

1. Generation 0: Short-lived objects.
2. Generation 1: Medium-lived objects.
3. Generation 2: Long-lived objects.

Example:

 class Program
{
    static void Main()
    {
        // Force garbage collection
        GC.Collect();
        GC.WaitForPendingFinalizers();
    }
}

 

16. What is the difference between Dispose() and Finalize()?

• Dispose():
  • Part of the IDisposable interface.
  • Must be called explicitly to release unmanaged resources.
• Finalize():
  • Called by the Garbage Collector before an object is destroyed.
  • Cannot be called explicitly; handled by the system.

Example:

 class MyClass : IDisposable
{
    public void Dispose()
    {
        // Clean up unmanaged resources
    }
    
    ~MyClass()
    {
        // Finalizer (destructor) called by GC
    }
}

 

17. What is Reflection in .NET?

• Reflection allows programs to inspect and interact with object metadata at runtime.
• It can be used to dynamically create instances, invoke methods, and access fields and properties.

Example:

 Type type = typeof(SampleClass);
object instance = Activator.CreateInstance(type);
MethodInfo method = type.GetMethod("PrintMessage");
method.Invoke(instance, null);

 

18. What is ADO.NET?

• ADO.NET is a data access technology used to interact with databases (SQL, Oracle, etc.) in the .NET Framework.
• It provides data connectivity between .NET applications and data sources, allowing you to execute SQL queries, stored procedures, and manage transactions.

Components of ADO.NET:

• Connection: Establishes a connection to the database.
• Command: Executes SQL statements.
• DataReader: Reads data from a data source in a forward-only manner.
• DataAdapter: Fills DataSet/DataTable with data.
• DataSet/DataTable: In-memory representation of data.

Example:

 using (SqlConnection connection = new SqlConnection("connectionString"))
{
    SqlCommand command = new SqlCommand("SELECT * FROM Students", connection);
    connection.Open();
    
    SqlDataReader reader = command.ExecuteReader();
    while (reader.Read())
    {
        Console.WriteLine(reader["Name"]);
    }
}

19. What is the difference between DataReader and DataSet in ADO.NET?

• DataReader:
  • Provides forward-only, read-only access to data from a database.
  • Faster and more memory-efficient.
• DataSet:
  • In-memory representation of data that can be manipulated without being connected to the database.
  • Slower, but supports multiple tables and relationships.

 

 

20. What is ASP.NET?

• ASP.NET is a web application framework developed by Microsoft for building dynamic web pages, websites, and web services.
• It provides tools and libraries for building web applications with features like state management, server controls, and web forms.

Types of ASP.NET Applications:

• Web Forms: Event-driven development model with server-side controls.
• MVC (Model-View-Controller): A design pattern separating data, UI, and logic.
• Web API: Used for building RESTful web services.
• Blazor: Allows building interactive web UIs using C# instead of JavaScript.

Example (Web Forms):

 protected void Button_Click(object sender, EventArgs e)
{
    Label.Text = "Hello, ASP.NET!";
}

 

21. What are HTTP Handlers and HTTP Modules in ASP.NET?

• HTTP Handlers:

  • Low-level components that process incoming HTTP requests directly.
  • Typically used to handle requests for specific file types (e.g., .aspx, .ashx).

• HTTP Modules:

  • Intercepts and modifies requests/responses at various stages in the pipeline.
  • Used for authentication, logging, or custom headers.

Example (Handler):

 public class MyHandler : IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        context.Response.Write("Handled by MyHandler.");
    }
    
    public bool IsReusable => false;
}

 

22. What is the difference between Session and ViewState in ASP.NET?

• Session:
  • Stores user-specific data on the server.
  • Persists across multiple pages and requests within a session.
  • Consumes more server resources (memory).
• ViewState:
  • Stores data in a hidden field on the client (browser) side.
  • Retains data only for a single page during postbacks.
  • Increases page size but doesn’t use server memory.

Example of ViewState:

 // Storing value in ViewState
ViewState["UserName"] = "John";

// Retrieving value from ViewState
string userName = ViewState["UserName"].ToString();

 

23. What is ASP.NET MVC?

• ASP.NET MVC is a web development framework that follows the Model-View-Controller design pattern.
  • Model: Represents the application data and business logic.
  • View: Displays the data and the user interface.
  • Controller: Handles user input, updates the model, and selects a view to render.

Advantages:

• Separation of concerns.
• Easier unit testing.
• Greater control over HTML, CSS, and JavaScript.

Example:

 public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }
}

 

24. What are Action Filters in ASP.NET MVC?

• Action Filters allow you to execute code before or after an action method is executed.
• Common use cases include logging, authorization, and caching.

Types of Action Filters:

• Authorization Filters (e.g., Authorize).
• Action Filters (e.g., OnActionExecuting, OnActionExecuted).
• Result Filters (e.g., OnResultExecuting, OnResultExecuted).
• Exception Filters (e.g., HandleError).

Example:

 public class LogActionFilter : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Log before action executes
    }
}

 

25. What is Entity Framework (EF)?

• Entity Framework is an Object-Relational Mapping (ORM) framework for .NET that allows developers to work with databases using .NET objects (classes) instead of writing SQL queries.
• Advantages:
  • Automatic generation of database schema.
  • Enables LINQ to query the database.
  • Database migration support for schema changes.

Example:

 // Defining a model
public class Student
{
    public int ID { get; set; }
    public string Name { get; set; }
}

// Using Entity Framework to interact with the database
using (var context = new SchoolContext())
{
    var students = context.Students.ToList();
}

26. What is the difference between LINQ to SQL and Entity Framework?

• LINQ to SQL:
  • Designed for direct database access with SQL Server.
  • Supports a one-to-one mapping between database tables and .NET classes.
  • Simpler but less feature-rich than Entity Framework.
• Entity Framework (EF):
  • Provides more features such as inheritance, complex types, and multi-table mapping.
  • Works with multiple database providers (SQL Server, MySQL, Oracle).
  • Supports Code First, Database First, and Model First approaches.

 

 

27. What is Web API in ASP.NET?

• ASP.NET Web API is a framework for building HTTP-based services that can be consumed by a wide variety of clients (e.g., browsers, mobile devices).
• Web API is primarily used to create RESTful services, where HTTP verbs (GET, POST, PUT, DELETE) map to CRUD operations.

 public class ProductsController : ApiController
{
    public IEnumerable<Product> GetAllProducts()
    {
        return productList;
    }
}

 

28. What is Dependency Injection (DI) in ASP.NET?

• Dependency Injection is a design pattern that allows injecting objects into a class, rather than creating objects inside the class.
• It decouples the creation of objects from the business logic, making the code more modular and testable.

Example (using ASP.NET Core DI):

 public class HomeController : Controller
{
    private readonly IProductService _productService;
    
    public HomeController(IProductService productService)
    {
        _productService = productService;
    }
    
    public IActionResult Index()
    {
        var products = _productService.GetProducts();
        return View(products);
    }
}

 

29. What are REST and SOAP?

• REST (Representational State Transfer):

  • Uses HTTP methods (GET, POST, PUT, DELETE).
  • Stateless communication.
  • JSON or XML as data format.
  • Simpler and more scalable for web APIs.

• SOAP (Simple Object Access Protocol):

  • Uses XML for request and response messages.
  • Requires more overhead due to its strict structure and protocols.
  • Supports security features like WS-Security.

 

 

30. What is OAuth in ASP.NET?

• OAuth is an open standard for token-based authentication, used to grant third-party applications limited access to user resources without exposing credentials.
• OAuth is commonly used in social logins (e.g., login with Google or Facebook).

31. What is SignalR in ASP.NET?

• SignalR is a library that allows real-time web functionality in ASP.NET applications.
• It enables the server to send updates to clients instantly via WebSockets, long-polling, or Server-Sent Events.

Use cases:

• Chat applications.
• Real-time notifications.
• Live data feeds.

Example:

 public class ChatHub : Hub
{
    public async Task SendMessage(string user, string message)
    {
        await Clients.All.SendAsync("ReceiveMessage", user, message);
    }
}

 

32. What is NuGet in .NET?

• NuGet is a package manager for .NET, allowing developers to share and consume reusable code libraries.
• It simplifies the process of including third-party libraries into your project.

Example:

 Install-Package Newtonsoft.Json

 

33. What are Generics in C#?

• Generics allow defining classes, interfaces, and methods with placeholders for data types.
• They promote code reusability and type safety by allowing you to create type-agnostic data structures.

Example:

 public class GenericClass<T>
{
    public T Data { get; set; }
}

 

34. What is a delegate in C#?

• Delegates are type-safe function pointers that allow methods to be passed as parameters.
• Useful in implementing callback functions, events, and asynchronous programming.

Example:

 public delegate void DisplayMessage(string message);

public void ShowMessage(string message)
{
    Console.WriteLine(message);
}

DisplayMessage display = new DisplayMessage(ShowMessage);
display("Hello, World!");

 

35. What are events in C#?

• Events provide a mechanism for a class to notify other classes or objects when something of interest occurs.
• Events are built on top of delegates and are typically used in UI programming and handling user interactions.

Example:

 public event EventHandler ButtonClicked;

 

36. What are Extension Methods in C#?

• Extension Methods allow you to add new methods to existing types without modifying their source code or creating a derived type.
• Extension methods are static methods, but they are called as if they were instance methods on the extended type.

Syntax:

 public static class StringExtensions
{
    public static int WordCount(this string str)
    {
        return str.Split(' ').Length;
    }
}

// Usage
string sentence = "Hello World";
int count = sentence.WordCount();  // Output: 2

Key Points:

• Defined in static classes.
• The first parameter specifies the type being extended, and the keyword this is used before the type.

 

37. What is the difference between finalize and dispose methods?

• Finalize:

  • Called by the garbage collector before an object is destroyed.
  • Used to release unmanaged resources.
  • Cannot be called explicitly in code.
  • Defined using a destructor in C#.

• Dispose:

  • Explicitly called by the developer to release unmanaged resources.
  • Part of the IDisposable interface.
  • Should be used when working with resources like file handles or database connections.

Example using Dispose:

 public class ResourceHolder : IDisposable
{
    private bool disposed = false;
    
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
    
    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                // Free managed resources
            }
            // Free unmanaged resources
            disposed = true;
        }
    }
    
    ~ResourceHolder()
    {
        Dispose(false);
    }
}

 

38. What is the using statement in C#?

• The using statement is used to automatically manage the disposal of unmanaged resources.
• It ensures that Dispose() is called on objects that implement IDisposable, even if an exception occurs.

Example:

 using (var reader = new StreamReader("file.txt"))
{
    string content = reader.ReadToEnd();
}
// `Dispose()` is automatically called on `StreamReader`.

 

39. What is a sealed class in C#?

• A sealed class cannot be inherited by other classes. It restricts the class hierarchy by preventing inheritance.
• Sealing a class can be useful for security, performance, or if you want to ensure the class’s implementation stays unchanged.

Example:

 public sealed class SealedClass
{
    public void Display()
    {
        Console.WriteLine("This is a sealed class.");
    }
}

 

40. What is the lock statement in C#?

• The lock statement is used to ensure that a block of code is executed by only one thread at a time. It provides thread-safety by preventing race conditions.
• Typically used when working with shared resources in multi-threaded applications.

Example:

 private static object _lock = new object();

public void CriticalSection()
{
    lock (_lock)
    {
        // Code that must be synchronized
    }
}

 

41. What are Indexers in C#?

• Indexers allow objects to be indexed like arrays. They enable a class to be accessed using square brackets [], similar to array elements.

Example:

 public class SampleCollection
{
    private string[] elements = new string[100];
    
    public string this[int index]
    {
        get { return elements[index]; }
        set { elements[index] = value; }
    }
}

// Usage
SampleCollection collection = new SampleCollection();
collection[0] = "First Element";
Console.WriteLine(collection[0]); // Output: First Element

 

42. What is the difference between Array and ArrayList in C#?

• Array:

  • Fixed size, strongly-typed (can only hold one data type).
  • Faster performance due to strong typing.

• ArrayList:

  • Dynamic size, but not strongly-typed (can hold different data types).
  • Uses more memory and is slower compared to arrays due to boxing and unboxing of value types.

Example:

 // Array
int[] numbers = new int[5];

// ArrayList
ArrayList list = new ArrayList();
list.Add(1);
list.Add("String"); // Mixed types

 

43. What is a Multicast Delegate in C#?

• A Multicast Delegate can hold references to multiple methods. When invoked, it calls all the methods in its invocation list.

Example:

 public delegate void Notify();

public class DelegateExample
{
    public static void Method1() { Console.WriteLine("Method1"); }
    public static void Method2() { Console.WriteLine("Method2"); }

    public static void Main()
    {
        Notify notifyDelegate = Method1;
        notifyDelegate += Method2; // Multicast
        notifyDelegate.Invoke();
    }
}

// Output:
// Method1
// Method2

 

44. What is the difference between IEnumerable and IQueryable in C#?

• IEnumerable:

  • Suitable for in-memory data collection.
  • Queries are executed in memory.
  • Supports LINQ to Objects and LINQ to XML.

• IQueryable:

  • Suitable for out-of-memory data (e.g., databases).
  • Queries are executed on the data source (e.g., SQL database).
  • Supports deferred execution and LINQ to SQL.

Example:

 // Using IQueryable for deferred execution
IQueryable<Product> query = dbContext.Products.Where(p => p.Price > 50);

// Using IEnumerable
IEnumerable<Product> products = query.ToList();

 

45. What are anonymous methods in C#?

• Anonymous methods allow you to define inline, unnamed methods using the delegate keyword.
• They are used for shorter, simpler delegate expressions, and can capture variables from their surrounding scope.

Example:

 Func<int, int> square = delegate (int x)
{
    return x * x;
};

int result = square(5);  // Output: 25

 

46. What are Lambda Expressions in C#?

• Lambda expressions are concise ways to write anonymous methods. They are used extensively in LINQ queries.

Example:

 Func<int, int> square = x => x * x;

int result = square(5);  // Output: 25

 

47. What is the role of yield in C#?

• yield allows methods to return elements of a collection one at a time, without storing them all in memory. It's useful for creating custom iterator methods.

Example:

 public IEnumerable<int> GetNumbers()
{
    for (int i = 1; i <= 5; i++)
    {
        yield return i;
    }
}

// Usage
foreach (int number in GetNumbers())
{
    Console.WriteLine(number);
}

 

48. What is Reflection in C#?

• Reflection allows inspecting and interacting with the metadata of types, methods, and properties at runtime.

Use cases:

• Creating objects dynamically.
• Invoking methods at runtime.
• Accessing private fields and methods.

Example:

 Type type = typeof(MyClass);
MethodInfo method = type.GetMethod("MyMethod");
method.Invoke(Activator.CreateInstance(type), null);

 

49. What is the purpose of is and as operators in C#?

• is: Checks if an object is of a specific type.
• as: Attempts to cast an object to a specific type, returning null if the cast fails.

Example:

 object obj = "Hello";

if (obj is string)
{
    string str = obj as string;
    Console.WriteLine(str);
}

 

50. What is the out keyword in C#?

• The out keyword allows a method to return multiple values by passing arguments by reference.
• Parameters marked with out must be assigned a value before the method returns.

Example:

 public void GetValues(out int a, out int b)
{
    a = 10;
    b = 20;
}

// Usage
int x, y;
GetValues(out x, out y);
Console.WriteLine($"x = {x}, y = {y}");

 

51. What is a Strong Name in .NET?

• A Strong Name uniquely identifies an assembly using its name, version, culture, and public key token.
• Strongly named assemblies are stored in the GAC and help in avoiding conflicts between versions.

Example:

 sn -k MyKey.snk

 

52. What is the difference between const and readonly in C#?

• const:
  • Compile-time constant.
  • Value cannot change.
  • Must be assigned at declaration.
• readonly:
  • Runtime constant.
  • Can be assigned at runtime in the constructor.

Example:

 const int maxItems = 100;
readonly int maxLimit;

 

53. What is the purpose of sealed methods in C#?

• A sealed method is a method that prevents overriding in derived classes.
• Only applies to methods in base classes marked virtual or override.

Example:

 public override sealed void Method()
{
    // This method cannot be overridden further.
}

 

54. What is the difference between throw and throw ex in exception handling?

• throw: Re-throws the original exception while preserving the stack trace.
• throw ex: Resets the stack trace, making it harder to trace the original error.

Example:

 try
{
    // Some code
}
catch(Exception ex)
{
    throw; // Preserves original exception
}

 

55. What is the difference between Task and Thread in C#?

• Task: Higher-level abstraction for managing asynchronous operations. It supports continuations and better integrates with async/await.
• Thread: Lower-level, represents a unit of execution in the system.

 

 

56. What is Lazy<T> in C#?

• Lazy<T> provides a way to delay the initialization of an object until it is needed (lazy loading).

Example:

 Lazy<MyClass> lazyObj = new Lazy<MyClass>(() => new MyClass());

 

57. What is the difference between Abstract Class and Interface in C#?

• Abstract Class:
  • Can have method implementations.
  • Supports access modifiers.
  • Can contain constructors.
• Interface:
  • Only method declarations (before C# 8.0).
  • Cannot have access modifiers.
  • No constructors.

 

58. What is the difference between synchronous and asynchronous programming?

• Synchronous:
  • Blocking, one operation must complete before another can start.
• Asynchronous:
  • Non-blocking, allows operations to run in parallel or independently.

Example:

 await Task.Delay(1000); // Asynchronous call

 

59. What is the Func delegate in C#?

• Func is a built-in delegate type that returns a value. It can take up to 16 input parameters.

Example:

 Func<int, int, int> add = (x, y) => x + y;

 

60. What is the difference between String and StringBuilder?

• String: Immutable, every change creates a new string object.
• StringBuilder: Mutable, optimized for multiple manipulations on strings.

 

 

61. What is the Singleton Design Pattern?

• The Singleton Pattern ensures that a class has only one instance and provides a global point of access to it.

Example:

 public class Singleton
{
    private static Singleton _instance;
    private Singleton() { }

    public static Singleton Instance => _instance ??= new Singleton();
}

 

62. What is Memory Leak in .NET and how to prevent it?

• A Memory Leak occurs when objects are no longer used but not freed, causing memory exhaustion.
• To prevent it:
  • Dispose unmanaged resources properly.
  • Use weak references where applicable.
  • Implement the IDisposable interface.

 

63. What is the difference between Task.Run() and TaskFactory.StartNew()?

• Task.Run(): Suitable for CPU-bound operations and preferred for new code.
• TaskFactory.StartNew(): Offers more configuration options and is more flexible.

 

64. What is the volatile keyword in C#?

• The volatile keyword ensures that a variable's value is always read from memory, preventing optimizations that might cache its value in CPU registers.

 

65. What is the difference between Task.Wait() and Task.Result?

• Task.Wait(): Blocks the calling thread until the task completes.
• Task.Result: Blocks the thread and retrieves the task’s result.

 

66. What is the difference between a Shallow Copy and a Deep Copy?

• Shallow Copy: Copies the reference types as references (pointers).
• Deep Copy: Copies the actual objects, creating new instances.

 

67. What is the difference between a List<T> and an Array in C#?

• List<T>: Dynamic size, resizable, part of System.Collections.Generic.
• Array: Fixed size, cannot resize after creation.

 

68. What are Nullable Types in C#?

• Nullable types allow value types to have null values, using the ? syntax.

Example:

 int? num = null;

 

69. What is the difference between First() and FirstOrDefault() in LINQ?

• First(): Throws an exception if no element is found.
• FirstOrDefault(): Returns a default value (like null or 0) if no element is found.

 

70. What is yield in C#?

• yield is used to create an iterator block, returning each element of a collection one at a time without creating the entire collection in memory.

 

71. What are the differences between Task and ThreadPool?

• Task: Used for managing parallel code.
• ThreadPool: Manages a pool of worker threads to perform tasks.

 

72. What is the lock keyword in C#?

• lock is used to ensure that a block of code runs exclusively in a multi-threaded environment, preventing race conditions.

 

73. What is IEnumerable<T> in C#?

• IEnumerable<T> represents a forward-only, read-only collection of a sequence of elements.

 

 

74. What is Covariance and Contravariance in C#?

• Covariance allows a method to return a more derived type than the specified type.
• Contravariance allows a method to accept arguments of a more general type than the specified type.

 

75. What is a Mutex in .NET?

• A Mutex is used for synchronizing access to a resource across multiple threads and processes.

 

76. What are Tuples in C#?

• A Tuple is a data structure that can hold multiple values of different types.

Example:

 var tuple = Tuple.Create(1, "Hello", true);

 

77. What is the difference between ToString() and Convert.ToString()?

• ToString(): Can throw an exception if the object is null.
• Convert.ToString(): Returns an empty string if the object is null.

 

78. What is the ThreadLocal<T> class in C#?

• ThreadLocal<T> provides thread-local storage, meaning each thread has its own separate instance of a variable.

 

79. What is the ICloneable interface in C#?

• The ICloneable interface provides a mechanism for creating a copy of an object.

 

80. What is the WeakReference class in C#?

• A WeakReference allows an object to be garbage collected while still allowing a reference to the object.